Tuberculosis & HIV

TB is the most common opportunistic infection for HIV and the leading cause of HIV-related
deaths.

Once regarded as a disease of poverty, tuberculosis, which is estimated to have infected
one-third of the world’s population, is now seen primarily as a disease of disparities—ethnic,
racial, geographic, economic, biological. Most of the nine million new cases of TB
that emerge each year occur in just 22 “high-burden” countries, chief among them China
and India. Prison populations are especially vulnerable, as are people infected with
HIV. TB is, in fact, the most common opportunistic infection for HIV and the leading
cause of HIV-related deaths.

Yang has spent almost two decades studying TB. She’s especially interested in the
biology of latent-TB infection, which can reside in people for as long as 30 years
before awakening to wreak bodily havoc. Despite decades of research, the biological
basis of this phenomenon remains poorly understood. Yang’s research has implications
for the development of vaccines to prevent latent-TB infection from reactivation and
drugs to eliminate the latent-TB bacillus from infected hosts.

What triggers the reactivation of latent TB? The host-immune system almost certainly
has an effect, Yang says. Malnutrition can compromise immunity, as can exposure to
other pathogens, such as HIV. A person’s genetic, social, and economic status also
contributes. “That’s why my future goal for research is really to integrate host-pathogen,
environmental, and societal factors,” she explains.

Yang’s research will inform and enrich the World Health Organization’s “Global Plan
to Stop TB,” an ambitious campaign to eliminate the disease by 2015. “The more we
do, the more leads we have, and the more new research directions,” Yang says. “Sometimes
I get so excited.”

factCheck

One-third of the world’s current population is estimated to be infected with TB bacilli

Five to ten percent of people who are infected with TB bacilli become sick or infectious
at some time in their life

People with HIV and TB infection are much more likely to develop active TB

TB is the leading cause of death among HIV-infected individuals

Worldwide, TB is the leading killer of women, outranking all other causes of maternal
mortality

TB disproportionately affects people in resource-poor settings, especially those in
Asia and Africa